For an alternate-current type PDP and a display device of the PDP, stabilization of discharge (discharges in a discharge space and display cell) in the PDP is an important technique. To stabilize the discharge, a PDP structure and a material by which discharge is fired at a further lower voltage and plenty of priming particles (electrons) are supplied to the discharge space are necessary.
As the PDP structure and material for the purpose, a film (layer) of magnesium oxide (MgO) has been conventionally used to a surface being in contact with (exposed) to discharge (discharge space).
For example, there is a structure in which a protective layer (discharge protective layer) of MgO is provided on a dielectric layer of a front plate structure in a PDP. Also, there is a structure in which a priming-particle-emitting powder (layer) of MgO crystal powder or the like is further provided on the protective layer.
While the above-mentioned MgO film is a material sufficiently working and effective, a material which outperforms MgO (effects of a discharge voltage reduction etc. by MgO) is needed to further improve display characteristics of PDPs.
As a material for the further improvement, strontium oxide (SrO), calcium oxide (CaO) and the like have been already found out as materials which lower the discharge voltage. However, films (low-discharge-voltage films) formed of these materials are unstable in the air, and thus they cannot be handled well as they are in the manufacturing process.
To handle the films of the above-mentioned materials such as SrO and CaO well, as described in Japanese Patent No. 3073451 (Patent Document 1), there has been suggested a method in which a surface of the film of any of these materials after deposition is covered with an inactive (inert) film (air barrier layer (temporary protective film)) so that reaction in the air (reaction with moisture, carbon-rich gas etc.) is suppressed (prevented), and the inactive film is removed after panel assembly.
In addition, the following is a supplementation to the above discharge stabilization (discharge delay improvement). Along with achievement of higher definition of the PDP, to shorten an address period, it is effective to reduce a width of an applied voltage pulse. However, there is a variation in the time (discharge delay) from application of a voltage (e.g., address voltage) to generation of a discharge (e.g., address discharge). Thus, when the width of the applied voltage pulse is small, there is a possibility that discharge may not be generated even the pulse is applied. In that case, as display cell are not turned ON properly, an image quality degradation will be posed. As a means for improving the above-mentioned discharge delay, there is a technique of providing MgO crystal (layer) as a priming-particle-emitting powder (layer) to be exposed to a discharge space in a front plate structure. Such a technique is described in, for example, Japanese Patent Application Laid-Open Publication No. 2006-59786 (Patent Document 2).
Patent Document 1: Japanese Patent No. 3073451
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2006-59786